1. Field of the Invention
This invention relates to a pulse-controlled power converter, its associated controller, and an electric motor controller implementing such converters.
2. Discussion of the Related Art
Such converters are used, for example, in electronic motor controllers, which include electronic power switches in a bridge arm or full-bridge configuration.
Electronically controlled motors are utilized in many applications. Until recently, however, the development of certain applications has been slowed down due to the cost of the converters. In fact, the cost of implementing the necessary power components remained relatively high until a few years ago.
The recent availability of MOSFET power transistors has opened the way to the development of good quality dc-to-ac converters, and the ease with which they can be employed makes them a particularly attractive solution. Additionally, it is known to use converters controlled by a digital system.
Such converters have a low-voltage level (lower stage of bridge arms), the development of which presents no particular difficulties. The digital control unit can be associated with a power amplifier such as a MOSFET power transistor.
The development of the high-voltage circuit (upper stage of bridge arms) is, however, more delicate because of the potential difference that exists between the gate control circuit and the digital control unit. Various solutions have been proposed to implement this circuit.
According to a first solution, high-voltage integrated circuits are used, possibly in conjunction with standard integrated components. The cost of these high-voltage integrated circuits is, however, relatively high, and is not expected to fall significantly in the coming years. Moreover, in order to function, such devices require supplemental circuits such as floating auxiliary power supplies.
Another solution includes using a small high-frequency transformer which is located between each gate control circuit of the MOSFET power transistor and the digital control unit. The primary circuit of this transformer is controlled by a high-frequency signal, the secondary circuit thereof includes a special circuit for driving the gate of the MOSFET power component.
According to a third solution, the input capacitance of the MOSFET power component is used as a passing state memory. In the blocked state, the memory uses a supplemental capacitor. To achieve this, the pulse transformer only requires a few turns.
The object of the present invention is to produce a satisfactory synchronizing pulse-controlled converter as simply as possible, i.e., at a very low cost.
To achieve this objective, it is considered both desirable and possible to provide the digital control unit with a large number of functional features while keeping the operation of the high-voltage circuit as simple as possible.